Process for separating halogenated hydrocarbons by gas-liquid separation with a solvent

ABSTRACT

A PROCESS FOR SEPARATING 1,1,2-TRICHLOROTRIFLUOROETHANE AND 1,2-DICHLORO- 1,1-DIFLUOROETHANE AND FOR SEPARATING 1,2-DICHLOROTETRAFLUORETHANE AND 1-CHLORO - 1,2,2 - TRIFLUOROETHANE BY ADDING AN EXTRANEOUS VOLATILITY-MODIFYING AGENT AND THEREAFTER SEPARATING SAID COMPOUNDS IN THE PRESENCE OF SAID AGENT BY A GAS LIQUID SEPARATION PROCESS.

United States Patent 615cc 3,689,373

Patented Sept. 5, 1972 absorption depending on the system and the purity of 3,689,373 products desired. PROCESS FOR SEPARATING HALQGENATED We have found that the 113-132b pair can be separated HYDROCARBONS BY GAS-LIQUID SEPARA- TION WITH A SGLVENT William M. Hutchinson, Bartlesville, Okla, assignor to by a gas-liquid separation process in the presence of a volatility-modifying agent such as, for example, sulfolane Phimps Petroleum Company or an N-alkylpyrrolidone, as shown by the following data. No Drawing. Filed May 10, 1971, Ser. No. 141,981 EXAMPLE I CL C07c 17/38 Claims Separation of the 113-132b by simple distillation in the 10 presence of sulfolane was demonstrated by blending 46.3 grams of 113-1321) mixture (contained 59.3 wt. percent ABSTRACT 1 THE DISQLQSU'RE 132b, 39.1 wt. percent 113, and 1.6 Wt. percent 123a A process for separating 1,1,Z-trichlorotrifluoroethane 2 2) i lgdki-li r t t fi- -fl1 d i i1f gr s with 177.6 grams of sulfolane and distilling the blend from 0 e m uoroe am a t a SOO-ml. flask attached to a condenser. A simple d1st1lfluomethane by adding an extfaneous volatility'modify lation was then performed without reflux. The following mg agent and thereafter separating said compounds in the data were taken.

presence of said agent by a gas-liquid separation process.

TABLE I Overhead distillate This invention relates to the separation of halogenated C0mpO$iti(;;1, E hydrocarbons of a first m xture, more particularly, to a O h d t Temperature," Percent process for separating 1,2-dichlorotetrafluoroethane from gg f cu Overhead Kettle Wt 1239, 3 1, 13 a mixture of 1,Z-dichlorotetrafluoroethane and l-chloro- 51 62-66 1. 4. 'lr. 29 71 1,2,2 tr1fluoroethane and separating 1,1,2 trichlorotri- 5L5 66.73 r, 31 69 fiuoroethane from a mixture of 1,1,2-trichlorotrifluoro- 73-84 1 38 61 51. 5 84-100 6.9 1 50 ethane and 1,2-d1chloro-1,l-difluoroethane. 20 5, 1 70 29 In order to simplify the description of this process, gg-g 2:;83 Z; 89 11 1,1,2 trichlorotrifiuoroethane is hereafter referred to as @1111: m i fi 131,9 96 8:5 $1962 113; 1,2-dichlorotetrafiuoroethane is hereafter referred to as 114; 1,Z-dichloro-1,1-difluoroethane is hereafter referred to as 132b; and l-chloro-1,2,2-trifiuoroethane is hereafter 1 Analyses by gas-liquid chromatography.

referred to as 131 The above data indicate that 113 is much more volatile In various hydrocarbon processes known in the art, in the presence of sulfolane than 132b and thus may be mixtures of 114 and 133 and mixtures of 113 and 132b oveFhfiad m a gasdiquid, separamln Process of are formed It sometimes then becomes necessary to tractive distillation or gas-liquld absorption type. Use of arate the halogenated hydrocarbons of the mixture for a longer column contammg Stages should Produce recovering the valuable constituents or for further procan overhead Product approachmg 100% 113 whlle essing. An example source of the 114-133 first mixture is mining (as Shown by data in Table a bottoms Product found as a product of the electrochemical fluorination of of 132bethylene dichloride and an example source of the 113 EXAMPLE H 132b first mixture is also found as a product of the electrochemical fluorination of ethylene dichloride. The proc- It was slmllarly l q f f that 113 Could be ess of electrochemical fluorination of ethylene dichloride mated f 1321) by dlstlnauop m the presence of Nqneth' is known in the art and is not a part of this application and yl'pynqhdone (NMP) In i test grams of 113- it should be understood that the halogenated hydrocar- 132b mlxture (Same blerid m .Example I) was added to bon separation process of this invention can be utilized of NMP and m m the same Column used without regard to the process by which the halogenated m Example The followmg data were taken: hydrocarbon mixture was obtained. TABLE In their separated form, the constituents of the first 50 Temperatureya Overhead distillate 25:? have bollmg pomts at atmospheric pressure as iiriiii i out Overhead Kettle Wt.,g. 123a 132b 113 -99 14.0 Tr. 37.6 62.4 99-112 7.5 1.3 45.1 53.5 are; it it at Mixture Constituent point, C. 132 142 711 8 2 i112 114.133 11% 3.6 The above data indicate that 113 can be separated from 132b by distillation in the presence of NMP as a volatil- 60 ity-modifying agent although the separation was not as The relative volatility of the 113-132b mixture is only great as in the presence of sulfolane. More gas-liquid con- 1.01. tacting stages are needed for NMP than for sulfolane.

The relative volatility of the 114-133 mixture is slight- It was demonstrated that 114 could be separated from ly higher. Separation of these mixtures by ordinary dis- 133 by a gas-liquid absorption process using as volatilitytillation is therefor difficult. It is therefore advantageous 5 modifying agents acetone, benzonitrile, 3-methyl-sulfolane, to modify the relative volatility of the components by the and sulfolane. A As-inch-diameter glass column with a addition of an extraneous agent. By this means one comheight of 32 inches was packed with stainless steel packponent becomes more or lessvolatile than the other coming to a height of 27 inches and used as the gas-liquid ponent and separation is possible using a reasonable nurnseparation column. The solvent was passed to the top of her of vapor-liquid contacting trays in a gas-liquid separa- 7 the column and passed downward through the packing. tion process. The actual separation process used may be The gaseous 114-133 mixture was passed upward through extractive distillation, azeotropic distillation, or gas-liquid the column countercurrently to the descending solvent.

.3 The gaseous effiuent (raflinate) from the top and the solvent bottoms (extract) were analyzed by gas-liquid chromatography for 114, 133, and other halogenated hydrocarbons present in smaller amounts. The following data were obtained:

4 2. A process, as set forth in claim 1, wherein the gasliquid contacting process is an extractive distillation process.

3. A process, as set forth in claim 2, wherein the solvent is sulfolane.

TABLE III Gas rate, solvetnt liter/min. Composition, wt percent Ti]. 8, Solvent ml [min Feed Raflinate Sample 114 124a 133 14221 li ee i i u uu 31% 9.7 0.8 1.2 0. 74 0.108 0. 040 a 0 Acet0ne...:;... 0.70 0.108 0.072 :33: 2% kg 3 108 M72 l xt m nn 53. 7 18.2 13.0 1.3 1 23 0.123 0.078 a 0 Benzonltrlle do 92.8 7.2 0.01 0 0-123 0-076 lflixtgaet g 10.7 10.5 1. 7 2.90 0.107 0. 001 a 0 0 3-methy1sulf0lane. {Nude 96.6 3.4. 0.01 0 0-107 0-070 llfilxli'iriactt nu 5 13.0 21.3 2.3 2 9 (L112 [L072 3. na 3-... .8 3.2 0.05 0 Su1folane. n -110 95. 0 4. 5 0.05 0 M12 0-082 {Extract 20.1 11.0 20.5 5.3

l Solvent-free basis.

1 Includes solvent.

No'rn.124a= CHFzC ClFz; 142a= CHClzCHzF.

The above data indicate that a significant separation was made between 114 and 133 by gas-liquid absorption using the 4 solvents listed. Additional separation would be obtained by use of longer columns containing additional separation stages. The gas-liquid absorption column is easily converted to an extractive distillation column by adding a reboiler to the base of the column and thus generating stripping vapor for that section of the column below the point of gaseous feed entry. Thus the data demonstrate that 114 and 133 can be separated by either gasliquid absorption or by extractive distillation using as extraneous agents sulfolane, acetone, benzonitrile, and 3- methylsulfolane.

Other modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing discussion and examples, and it should be understood that this invention is not to be unduly limited thereto.

What is claimed is:

1. A process for separating 1,1,2 trichlorotrifiuoroethane from a first mixture of 1,1,2-trichlorotrifluoroethane and 1,2-dichloro-1,1-difluoroethane, comprising:

adding a solvent selected from one of acetone, benzonitrile, sulfolane, 3-methylsulfolane, or mixtures thereof for forming a resultant second mixture; and

separating 1,1,2-trichlorotrifiuoroethane from the 1,2-

dichloro-1,1-difluoroethane of said second mixture by a gas-liquid contacting process.

UNITED STATES PATENTS 3,236,030 2/1966 Von Tress -71 3,282,801 1l/1966 Wust 20362 3,406,099 10/1968 Buckman et a1. 203-62 3,391,201 7/1968 Jaeger 203-58 3,488,920 l/1970 Hutchinson 557l 3,624,166 11/ 1971 Fuhrmann 260653 WILBUR L. BASCOMB, JR., Primary Examiner US. Cl. X.R. 

